JPH0114921B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for polymerizing a gaseous monomer or a mixture of gaseous and liquid monomers in which the degree of loading is determined continuously by regularly occurring pressure changes and by using an automatic measurement and control system. The invention relates to a process for the continuous production of polymer dispersions by carrying out polymerization in the presence of a liquid phase in a reactor which is maintained at a constant temperature. In particular, this invention relates to an improved continuous process for the production of aqueous dispersions of ethylene homopolymers and copolymers. By degree of filling herein is meant the percentage of the reactor volume occupied by the liquid phase. It is therefore the volume ratio of the liquid phase to the total volume of the reactor multiplied by 100. Strict adherence to special, predetermined loading degrees is
It is of great importance for continuous polymerization in heterogeneous phases. For example, when a constant flow of reacting substances is metered into a vessel in a reactor, assuming a steady state of reaction, the amount of heat generated per unit time is independent of the degree of loading of the reactor. is possible. How this amount of heat is distributed in the reactor over time and how it is removed depends, among other things, on the degree of loading with the reaction mixture. The ratio of the amount of heat generated per unit time to the cooling surface of the reactor wall also varies depending on the degree of loading of the reactor. In continuous processes, the average residence time of the reaction mixture also depends on the reactor loading or degree of loading, so when determining the amount fed, the average residence time is lower the lower the degree of loading of the reactor. Of course, it will be shorter. Furthermore, other factors determining the reaction process and product properties depend on the average residence time in the reactor. Therefore, it appears to be irrelevant whether the reactor is operated completely full or with a gas cushion as a buffer. The degree of loading of the reactor can often be readily determined by measuring the loading.
The loading specifies to what height the liquid phase is present in the reactor, from which the degree of loading can be calculated if the geometry and volume of the reactor are known. However, it is only possible to accurately determine the loading amount when the liquid surface is horizontal or when there is at least a precise phase limit between the liquid and gas phases. If the liquid is stirred or shaken in the container, the degree of loading can no longer be easily determined from the level of the liquid. Even if the liquid is agitated very regularly and well-defined bodies of revolution are formed, the volume of this liquid structure is not just a function of height, but a function of several variables. Now, when variable stirring speeds, turbulence, foam formation and chemical reactions are also taken into account, the mathematical determination of liquid volume from the level readable outside the reactor becomes a particularly open problem. In such cases, one must rely on experimental gauge pressure measurements. Many methods are known for determining the loading in a container. They are for example “Handbuch der
Industriellen MeBtechnik” (P.Profos.Vulkan
Verlag, Essen, 1974, pp. 289-303). Thus, the following means and methods may be listed: mechanical and electromechanical methods, for example methods of measuring the change from direct to alternating current resistance, hydrostatic and pneumatic methods, ultrasound methods, radioactive loading determination methods. Measurements, measurements using load cells, thermal detection methods and stationary and inspection optics. However, these known loading measurements assume a horizontal and stationary liquid surface. Agitation and foam formation interfere with mechanical and electromechanical methods. In case of vigorous stirring, the soaked float will move irregularly. At this time, the indication of the loading amount depends on the stirring speed. In the case of different stirring speeds, gauge measurements must be taken to determine the loading. A float immersed in liquid must, of course, not lose its free mobility. However, it often occurs that the float becomes coated and the product adheres, resulting in a jammed appearance. In this case, a loading amount with an error is indicated. Electrical, calorimetric or ultrasonic measuring sensors must likewise be protected from becoming coated with products in order to avoid erroneous readings. If the known charge measurement can be carried out without contact, or if the measuring sensor is contaminated by passing through the medium, as in the case of hydrostatic differential pressure measurements, radioactive charge measurements or load measurements using load cells. If it is not possible to enter the container, other prerequisites are necessary and are not necessarily met: The measurement of hydrostatic differential pressure is performed when a relatively very small hydrostatic pressure is superimposed on a very large pressure. This corresponds to an inherently difficult determination of a very small difference between two very large pressure values. Furthermore, the measurement is disturbed by stirring and vibration, and in particular by fluctuations in the total pressure. Radioactive measurements are performed without contact.
Thick tube walls and thick wall containers are not a problem. If there are two phases of different densities with distinct boundaries,
This method gives very good results. Radioactive loading measurement is one of the most possible methods.
It can be considered as one. However, for certain chemical reactions, if one expects virtually ideal mixing in a pressurized vessel due to the considerable stirring effect, which is essential for reactions where emulsifiers and dispersants are optionally present, This measurement is not valid. There is no longer an abrupt change in density from liquid to gas phase, and there is no longer a clear "load". Controlling the loading amount using a load cell is also possible when the operating pressure is as high as 300 bar, such as in an autoclave, and the density is several times higher than the loaded material (density in most cases is approximately 0.7 to 1.3 g/cc). (approximately 20 to 40 times) heavy and unsuitable in the case of very heavy pressurized vessels where vibrations are imparted by stirring the equipment.
Furthermore, such a container installed on a load cell must be free-standing and must not be rigidly connected to other equipment. The use of inspection optics and stationary optics to determine liquid volumes ensures that the means for measuring these volumes will withstand the pressure in the container and will not cloud with product and become opaque after a short period of time. It is possible in some cases. This is usually the case when working with latex. That is, if the determination of the loading and even the degree of loading is accompanied by difficulties in the vessel in which the loading is recorded, the measuring conditions are substantially It becomes even more troublesome. When several quantities of streams are weighed and these streams have different agglomeration conditions, and also between these different substances, e.g. decrease or increase in volume, increase or decrease in pressure, generation or consumption of heat, and coagulation. Measurement conditions become particularly unpredictable when changes in physical or chemical properties occur, accompanied by changes in state, solubility, chemical characteristics, etc. The loading of pressure-resistant, continuously flowable and thoroughly mixed and agitated containers containing gas and liquid phases under elevated pressure (e.g. 200 bar) can be easily carried out in e.g. non-pressurized processes. It cannot be maintained constant by means of risers or laterally located overflow pipes, as is the case with conventional water systems. Therefore, in the case of pressurized vessels, the degree of loading or strict adherence to the loading amount is associated with considerable problems. For example, from DE 2007793, a dispersion produced in a bubble column reactor by thorough mixing with circulating gas and feeding into a separator is removed from a pressurized discharge channel and thereby A continuous process for the production of copolymers is known in which the expansion process is influenced by the loading in the separator and the time of the stroke of the two gate valves is controlled by a time relay (see, patent (Claim 4 and drawings on page 15).
However, the problem of controlling the total device loading is not completely solved by using occasional discharges of the separator. That is, the degree of loading of the device depends not only on the conditions in the separator but also on the conditions in the bubble column reactor. DE 2250517 describes a process for the production of ethylene-vinyl ester copolymers under pressure, which maintains the degree of loading of the polymerization reactor within special limits. In this regard, page 12 states that both the dispersion produced as well as the unreacted monomer are discharged from a suitable discharge system, thereby reducing the degree of loading by 50%.
It is stated that it must be ensured that it remains within the range of ~99.9%, preferably 65-99.9%. This method uses ethylene from 5 to
Use at 120 atmospheres, preferably 15-60 atmospheres. In this method, in order to ensure that the pressure regulated is defined by a certain excess of ethylene, 4
A ~25% excess of ethylene is preferred in the reactor. The polymer produced by this method is up to 55
It has an ethylene content of % by weight. In this method, 85 to 99.5
% of polymerization can be achieved. DE 2309368 discloses that during the production of the described dispersions, not only the pressure but also the degree of loading of the autoclave influences the proportion of ethylene in the copolymer. Related to this, Section 3 on page 17 states that the ratio of the volume of the dispersion liquid in the reactor to the total volume of the reactor is determined by an "appropriate control mechanism".
states that it can be maintained as constant as possible in the range of 0.7 to 0.95. Furthermore,
It is mentioned in paragraph 3 on page 14 that ``measuring the compressibility of the autoclave contents reveals the degree of loading of the reactor,'' i.e., by adding a defined amount of ethylene, the pressure is increased. It is proposed that the proposed compressibility measurement can be carried out using the following method: Fig. 1 shows the arrangement of the apparatus outlined in Fig. , that is, when following an arrangement in which ethylene is supplied from valve 2 controlled by the flow rate,
This is only possible manually. According to FIG. 1, when product is discharged from pressure-controlled valve 4 and ethylene is simultaneously fed in a controlled amount from valve 2, in order to perform compressibility measurements, the product discharge and ethylene Both supplies must be interrupted. This measurement therefore requires a short interruption of the manufacturing process. The above-mentioned interruptions in continuous production processes can only take place after relatively long intervals. At this time, a new supply amount of ethylene is determined according to these measurements. This method makes it possible to maintain the degree of loading of the autoclave within approximately the required range. However, in this method it is not possible to keep the degree of loading exactly constant, since the reaction products are removed in such a way that the pressure in the reactor remains practically constant;
As a result, a constant degree of loading is not guaranteed. Now, the degree of loading in continuous polymerization processes is determined continuously by the pressure changes occurring in the reactor by using automatic measurement and control systems and the supply of reaction components and/or removal of reaction products. It has been discovered that a constant predetermined value can be maintained if adjusted to a predetermined value by. Thus, the present invention provides for the presence of gaseous or gaseous and liquid monomers, in particular ethylene and optionally vinyl chloride and/or vinyl acetate, in a pressurized reactor in which the degree of loading is maintained constant. In producing preferably aqueous polymer dispersions by continuous polymerization, the degree of loading is induced into the reactor at a constant initial pressure and at a constant temperature by regular repetitions. automatic measurement and control of the addition of monomer and liquid phase and/or removal of reaction products, so that the degree of loading of the reactor remains constant. A method for producing the aqueous polymer dispersion is provided, in which the aqueous polymer dispersion is increased or decreased using a system. A suitable pressure change in the reactor can be created, for example, by briefly interrupting the supply of gaseous monomer and the removal of the reaction products and by injecting a determined amount of liquid into the reactor. . The resulting pressure increase depends on the volume of gas in the reactor and, as a result, on the degree of loading, which can be accurately determined. The degree of loading can be determined at any time by a predetermined gauge curve. In a similar manner, the degree of loading can also be determined, for example, by the decrease in pressure that occurs when a defined amount of liquid is removed. Appropriate pressure changes can also be brought about by increasing or decreasing the volume of gas in a limited way, for example by moving a piston connected to the reactor chamber. In the method of the invention, the required pressure changes and the determination of the degree of loading are carried out constantly at short time intervals by means of automatic measurement and control systems, and deviations in the degree of loading from the originally determined values are Constant correction is made by increasing or decreasing the amount of reaction components introduced into the reactor and/or reaction products removed. As a result of this, the possible deviation of the degree of loading from the required value is kept very small and the degree of loading remains essentially constant during the entire course of the continuous polymerization process. In an advantageous embodiment of the invention, changes in pressure are used to measure and control the degree of loading. In this case, the pressure change takes place in the reactor by discontinuous removal of product by successive strokes. As a result of filling the discharge chamber with product and simultaneously interrupting the supply of gas to the reactor, a constant and defined amount of liquid phase is removed from the reactor in each case. This results in a corresponding increase in gas capacity and a short period of pressure drop. This drop is used to measure the degree of loading. If the degree of loading is always constant and the supply of liquid phase to the reactor is regular, then the stroke withdrawal of the reaction products takes place at regular time intervals. However, if the degree of loading measured in each withdrawal stroke is higher or lower than a predetermined value, subsequent discharge strokes may be required due to more rapid or slower removal of product. The automatic measurement and control system is activated earlier or later so that the degree of loading is readjusted. The degree of loading can be kept constant in a particularly simple and effective manner, namely by constant measurements carried out on each ejection stroke and by correction of the degree of loading from time to time. The pressure drop corresponding to the required degree of loading, which is used as a measuring means to monitor the degree of loading and to keep it constant, is determined by first carrying out the ejection stroke at regular time intervals and in each case This can be easily verified by measuring the pressure drop that occurs. The process according to the invention is particularly suitable for carrying out the polymerization in the presence of an aqueous phase, ie for producing aqueous polymer dispersions or polymer emulsions. It can be used suitably for the polymerization of ethylene, optionally with other monomers, and for the preparation of corresponding homo- and copolymer dispersions of ethylene. The process is particularly suitable for producing aqueous copolymer dispersions of ethylene and vinyl chloride and/or vinyl chloride.
The process according to the invention results in a very regular polymerization process and produces fairly homogeneous polymers. 50
Polymer dispersions with high solids contents of weight percent and higher can be easily prepared. Surprisingly, the degree of loading of the same reaction vessel is approximately
In the continuous emulsion polymerization process of vinyl acetate and ethylene of the present invention by using the same chemistry, the same temperature, and comparable low pressure as in the semi-continuous operation except for maintaining a constant 75%, the introduced ethylene unit
It has been discovered that copolymers can be prepared that have a high molecular weight of 65% by weight and are soluble in toluene (see Example 10). Furthermore, when applying the method of controlling the degree of loading at a pressure of 200 bar and a temperature range of 60 to 80° C. to a vinyl chloride-ethylene copolymerization reaction,
It has also been discovered that dispersions can be produced with a solids content of 45-50% by weight and an ethylene content of the polymer of 30-40% by weight. German published patent no.
According to the method of No. 2309368, it is possible to prepare dispersions containing 45-60% by weight of solids of vinyl chloride-ethylene copolymers, which contain up to 30% of the introduced ethylene. Only % by weight, temperatures of 40-80% and high pressures of the order of 200 bar are used. A summary of the process of the invention is described with respect to automatically controlling the degree of loading in e.g. ethylene-emulsion (co)polymer processes: (b) a more regular polymerization process with the effect that the reaction mixture leaving the reactor varies very little in its composition; ( c) Polymerization temperature that is kept constant very effectively.
This is particularly important when producing high concentration polyethylene latexes. By strictly controlling the degree of loading, uncontrolled reaction processes are avoided; (d) reduced formation on the walls of the coating and reduced formation of aggregates; (e) exit from the reactor. Since the residual monomers, such as vinyl chloride and ethylene, are present in practically constant relative proportions, disposal of the residual monomers is easy. Residual monomer streams of this type can naturally be circulated more easily than waste gas streams which are constant in composition and vary; and (f) residual monomer adsorbed, absorbed or emulsified in the dispersion. The yield of polymer is increased because only the body parts still exit the reactor, preventing cleavage of the more easily compressible ethylene-rich upper layer in the reactor. Ethylene-rich vinyl chloride-ethylene copolymer dispersions and vinyl acetate-ethylene copolymer dispersions can be produced by the process of the invention and used on a large scale as pigment binders. self-crosslinking copolymers, i.e. suitable monomers with reactive groups;
For example, polymers containing N-methylol acrylamide and methacrylamide and the corresponding N-methylol ethers can also be prepared for this purpose. Soft, high molecular weight vinyl chloride-ethylene and vinyl acetate-ethylene copolymer dispersions can be used as grafting bases for impact-resistant plastic materials, especially when they are crosslinked with e.g. peroxides or divinyl compounds. can. Ethylene-vinyl acetate copolymers are particularly suitable as graft bases for vinyl chloride or for mixing with polyvinyl chloride. In each case, an improved impact resistant polyvinyl chloride is obtained which has, among other characteristics, substantially improved notched bar test toughness. In the polymerization process according to the process of the invention, it is advantageous to introduce a seed latex into the autoclave, since equilibrium in the subsequent polymerization reaction is achieved more quickly. The process according to the invention can be used for all polymerization processes in which gaseous monomers are polymerized in the presence of a liquid phase which may contain other monomers in dissolved or dispersed form. can. The method comprises a liquid phase which dissolves gaseous substances which are reactive or inert under the above-mentioned limit conditions only to a limited extent and which may contain other substances in dissolved or dispersed form. It can also be applied to other reactions that occur in the same volume or under volume contraction. In addition to the already mentioned ethylene and vinyl chloride, gaseous substances include olefins such as propylene, butene and isobutylene, conjugated dienes such as butadiene and isoprene, vinyl halides such as vinyl fluoride, and also reactive substances such as , carbon monoxide, acetylene, hydrogen halide, oxygen, hydrogen, hydrogen sulfide, sulfur dioxide,
Ammonia and alkyl halides such as methylene chloride may be mentioned. The substance that determines the pressure of the gas in the reactor may be an inert gas such as nitrogen or helium. The relationship between the degree of loading F of a pressurized vessel with an empty volume V _B at an increase or decrease in pressure and a change in volume ΔV follows the Van der Waals equation of state for different gas pressures in the receiver.
P _A can be determined. When the volume of gas in the receiver expands by a certain amount ΔV corresponding to the volume of the discharge device at the bottom of the container, and the charge of the container is a liquid in which the gas is insoluble or only slightly soluble (e.g. water) , the pressure drop ΔP due to a certain pressure, e.g. P _A = 100 atm or P _A = 200 atm), depends on the volume of a pressurized vessel (e.g. V _B = 42.0) and a certain temperature, depending on the degree of loading F. (eg 60, 70, 80°C). However, it is also possible to express the volume of the gas after expansion V + △V as a ratio to the volume before expansion, and by a predetermined value for V + △V/V, the decrease in pressure can be expressed at different pressures and temperatures. It is also possible to calculate Instead of using calculations, simple preliminary experiments can be used to determine the desired degree of loading F and the change in pressure ΔP that occurs at a predetermined pressure and temperature.
It can also be expressed as a change in volume ΔV. The change in pressure is the measured value in the method of the invention, ie the desired value that is aimed in each case in order to monitor and keep constant the degree of loading. FIG. 1 is a block diagram showing a specific example of the measurement and control method according to the present invention. Block 1 represents the determination of the pressure by the storage means; Block 2 represents the controller including the current pulse converter; Block 3 represents the control means. V ₁ , V ₂ , V ₃ : represent pneumatically controlled valves, C-1 : represent a pressure vessel having a volume V _B and equipped with a stirring device, X-1 : a discharge chamber having a volume △V A-1: represents the temperature control unit, : represents the supply of liquid components, : represents the supply of gas components, : represents the outlet of the product. During normal operation, valves V ₂ and V ₃ are open and valve V ₁ is closed. Container C-1 being stirred
Adjust the pressure of the gas using V ₃ so that it remains constant. When receiving a command from the control means, valve V ₂
and V ₃ are closed and valve V ₁ is opened, filling the discharge chamber with volume ΔV. Immediately before opening V ₁ , the pressure value is determined by the transducer of the container C-1 and converted into an electrical unit signal (block 1). This value is sent to memory 1 in block 1. When the discharge chamber is filled, the pressure in the container C-1 drops more or less considerably depending on its degree of loading. This new pressure measurement is recorded again and sent to memory 2 in block 1. Valve V ₁ then closes and V ₂ and V ₃ open.
The discharge chamber X-1 is emptied automatically by the compressed gas therein or from time to time by blowing in another gas stream, for example water vapor. Pressure vessel C-1 is then returned to its nominal pressure _P2 by supplying gas through _V3 . Between P ₂ maintained in the pressurized container C-1 whose pressure is controlled by V ₃ and the outlet of the discharge chamber,
There is a constant large pressure drop. Memory 1 and 2 located in block 1
The two signals are subtracted from each other and retained in the form of an electrical signal as the actual value of ΔP. In block 2, this actual value of ΔP is compared with the required desired value of ΔP, and this is applied to the control means of block 3 by adding a time delay (time-lag) to the difference.
delayed) signal. When ΔP rises, the ejection stroke occurs more quickly;
When ΔP decreases, it becomes slow. For the controller in block 2 which compares the actual and desired value signals and produces a continuous electrical signal according to the contrast difference, a commercially conventional electrical continuous controller can be utilized. . Continuous controllers functioning in a counting or metering type can be used as controllers. The selected amplification factor depends on the degree of loading. Generally, a high amplification factor is selected when the degree of loading is low, while a low amplification factor is selected when the degree of loading is high. The control signal is converted into pulses in a downstream connected current-to-pulse converter. This pulse activates the control means in block 3 as a control command. Control means are present in block 3. These ensure that the valves V ₁ , V ₂ and V ₃ open and close at the correct time and in the correct sequence needed to maintain the pressure and release mechanism. The flow diagram of FIG. 2 represents an installation for applying the method of the invention. C-1 is an autoclave equipped with a stirrer, a free volume of 42.7, a nominal pressure of 320 bar and a vane stirrer driven by a motor (speed can be controlled in the range L to 300 rpm). The autoclave lid has holes for introducing the necessary supply pipes, for example ethylene, and for the flow transported by pumps PU ₁ to _{PU 4} . and . A-1 represents the pressurized water temperature control unit, V-1 V-2 V-3 represents the pneumatically operated control valves for ethylene supply and product removal, PU ₁ PU ₂ PU ₃ PU ₄ is a weighing pump (operating at high pressures of the order of 350 bar) for supplying aqueous monomers, e.g. vinyl acetate, and emulsifier and activator solutions such as:
represents. “Aqueous emulsifier solution” Aqueous emulsifier solution includes, for example, anionic emulsifier,
Contains protective colloids, water-soluble monomers, monomers optionally containing crosslinking groups, inhibitors, heavy metal salts and buffer substances. "Activator Solution" An aqueous initiator solution, such as a peroxodisulfate, hydroperoxide or azo initiator.
The activator solution can be introduced directly into the lower, more aqueous "phase" through the riser or bottom valve, and as well as the activator solution and the aqueous emulsifier solution. "Activator Solution" An aqueous solution of a reducing component, such as a sulfite, bisulfite or formaldehyde-sulfoxylate, which forms a redox system with the oxidizing component of the activator solution. represents the supply of gaseous monomer, for example ethylene. represents product removal. Furthermore, the symbols in Figure 2 have the following meanings: PC: Pressure control means, PI: Pressure indication, FQIR: Indication of the amount of ethylene by indication and registration, LIRC: Indication of the extent of loading by registration and registration. indication (corresponding to blocks 1 to 3 in Figure 1); PIRC: pressure indication by recording and control; M: stirring motor; FI: determination of the amount of gas; LI: degree of loading as already explained herein. control, PI: initial pressure, P ₂ : pressure inside the pressure vessel. The following further describes FIG. 2: The autoclave C-1 is maintained at the desired internal temperature by means of a pressurized water temperature control device A-1, as measured in the aqueous phase within the reactor. A controller is preferably used in this case. In this way, possible exothermic and endothermic effects are balanced. The ethylene feed is maintained at a constant initial pressure P-1 by using a mechanical pressure controller. The pressure P2 in the vessel with stirrer is kept constant within a narrow range by means of two piston controls. The amount of ethylene introduced into the reactor and preheated at any time to the reaction temperature is recorded. The weighed flows are then recorded and summed in order to track the polymerization process over time. The liquid stream is introduced into the autoclave with stirring using pumps PU ₁ to _{PU 4} . A constant metering of these streams, in particular of the active solution, is then carried out over time. The crude dispersion liquid coming out of the discharge chamber X-1 is subjected to a degassing step. The dissipating waste gas is separated into individual components. These can be reused as monomers (circulation). Example 1 This experiment shows the relationship between the degree of loading F of the pressurized receiver and the amount of sample that must be removed to obtain a certain pressure drop. Agglomerate-free vinyl chloride-ethylene copolymer latex with a solids content of approximately 50% by weight
45100 g were previously cleaned with ethylene and then emptied and introduced into a 42.7 clean autoclave having an operating pressure of 320 bar and equipped with a bottom outlet valve and a loading connection unit in the lid. The density of this latex is p=1.12 (g/
cm ³ ) and p=1.10 (g/cm ³ ) at 60°C. The latex is then heated to a temperature of +60°C with stirring (120 rpm), and when the temperature reaches a predetermined value, ethylene is injected under pressure to increase the pressure to exactly 100°C.
Adjusted to bar (P _A ). A quantity of latex was removed through the bottom valve of the autoclave such that the pressure was reduced to exactly 95 bar (P _E ). The weight of the sample removed was determined. Ethylene was then injected under pressure to bring the pressure inside the autoclave back to 100 bar.
The next sample was removed and these operations continued until the pressure dropped to 95 bar. Table 1 shows the results of the measurements. In particular, the following are mentioned: number of sample series (column 1), pressure drop from P _A = 100 bar to P _E (see column 1; P _E is in most cases 95 bar, (in some cases more material was removed than corresponds to a pressure drop of 5 bar to speed up the process), the amount of each latex sample removed (column 3), the amount of material removed before each removal. Total amount of latex (4th
column), the amount of latex in the autoclave (column 5),
column), the volume of latex in the autoclave (column 6), the degree of loading F recovered in total (column 7), the gas volume in the receiver (column 8) and the volume of the latex sample removed (column 7). Column 9). Experiments show that the amount of latex that has to be removed to induce a certain pressure drop depends on how much latex is still present in the autoclave: the higher the degree of loading, the more Less product is present to achieve the predetermined pressure drop. Example 2 Instead of 45100g latex, 38800g latex
Example 1, except that g was introduced and stirred at 50 rpm.
The experiment was repeated. Measurements were again carried out at P _A =100 bar and an internal temperature of 60°C. The amount of latex,
It was determined again depending on the degree of loading in the autoclave which caused a pressure drop of 5 bar. The sequences in Table 2 corresponded completely to Table 1. Stirring speed had no significant effect on measuring the degree of loading. From Example 2 and Example 1, the pressure drop △P
By keeping constant F, we see the fact that the amount of product removed from the pressurized receiver is a measure of the degree of loading F of the autoclave containing this product.

【table】

【table】

Table: Example 3 In Examples 1 and 2, the product was removed at a certain pressure drop. In this example, a constant ejection chamber volume was predetermined. That is, the pressure drop was measured upon removing a certain amount of product and decreasing the degree of loading in each case. A discharge device X-1 with a capacity ΔV=0.110 was attached to the autoclave C-1 (42.7) (see FIG. 2). 40 kg of vinyl chloride-ethylene copolymer latex with density p=1.1 (g/cc, 65 DEG C.) were introduced into an empty autoclave cleaned with ethylene. The latex was then heated to 65° C. with stirring (120 rpm). When the predetermined temperature was reached, the ethylene pressure was exactly 200 bar. The discharge device was then activated and at regular time intervals a quantity of latex was removed from the autoclave. V ₃ and V ₂ were closed and V ₁ was opened to fill the discharge chamber X-1 (see Figure 2). The latex was then expanded in a measuring container following V ₂ and accurately weighed in this container. Through V ₃ the pressure P _A was again set at 200 bar. V ₃ and V ₂ were closed and the next discharge stroke was performed. The pressure drop occurring per discharge stroke was recorded in each case. ΔP=P _A −P _E (P _E : final pressure set after the ejection operation) became progressively smaller with an increase in the number of ejection strokes and with a consequent decrease in the degree of loading of the autoclave. According to the recorder diagram, a pressure drop record as shown in FIG. 3 was obtained. Table 3 presents the results of measurements on a series of release systems of this type. In Table 3, the following are mentioned: the number of ejection strokes (column 1), the amount of latex removed in 5 ejection strokes (column 2) and the amount of latex per stroke (column 3). ). This amount was divided by the ejection volume to obtain the "density" (column 4) of the non-uniform ejection chamber loading. Enter the total amount released in column 5,
The amount in the autoclave is shown in column 6. The numbers in columns 5 and 6 are the amount of latex introduced in grams, i.e.
Give 40000. Ignoring the compressibility of the liquid phase, the capacity of the latex in the autoclave can be calculated by dividing the weight of the latex by the density of the latex at 65°C and normal pressure, p = 1.1 g/cc (see column 7). . Degree of loading recovered in total F (column 8)
is calculated by dividing the latex volume after each fifth stroke of discharge by the volume of the autoclave, V _B (42700 cm ³ ), and the volume of gas remaining in the autoclave (column 9) is V _B - V _f1 =
Calculated from the formula for V _gas . Finally, let the found pressure drop △P be
△P calculated according to der Waals equation
compared with the value for In FIG. 4, ΔP is shown against the degree of loading. The continuous curve corresponds to the value calculated according to the ideal gas equation,
The first point shown is the measured value found. From this series of measurements, it must be mentioned in particular that the amount of latex ejected per ejection stroke also decreases with a decrease in the degree of loading of the autoclave. Therefore, the "density" of the ejecting (heterogeneous) medium also decreases continuously.
Therefore, no sudden changes in "density" occur. Nevertheless, the degree of loading measurement according to the invention with respect to the ΔP to be measured provides reliable information regarding the degree of loading of the autoclave. V _gas only in the volume of the discharge chamber and in the autoclave: V _f1
The ratio of is decisive for the pressure drop. These series of measurements also demonstrate why other measurement methods for measuring loading that assume discontinuous liquid-vapor phase transitions in the final analysis are inadequate. The “density” (reference column 4) of the ejected medium is:
It changes from a value of 1.07 to 0.71 g/cm ³ while decreasing continuously.

【table】

Table Example 4 Emulsion Polymerization of Ethylene Controlled by Degree of Loading A clear solution 600 of the following ingredients was prepared: Deionized water 95.132 parts by weight Sodium methallylsulfonate 0.956 parts by weight C ₁₂ -C ₁₈ alkyl sulfone acid sodium
1.912 parts by weight anhydrous Na ₂ CO ₃ 1.000 parts by weight K ₂ S ₂ O ₈ 1.000 parts by weight 100.000 parts by weight 36.0 kg of polyethylene latex of density 0.96 (20 °C) with solids content 42% by weight (〓 degree of loading
87.8%) was introduced into a 42.7 autoclave corresponding to FIG. The autoclave was equipped with a stirring device, an ethylene feed line, an aqueous solution feed line, a discharge device (volume=0.100), an expansion vessel and a gas scale, and the measurement and control devices described above. The air in the autoclave chamber was purged with ethylene, the autoclave was closed, and heated to 80°C. When the above temperature was reached, ethylene was injected under a pressure of 200 bar. Now the aqueous emulsifier-activator solution defined above is
It was pumped in regularly at 3.0/hr (volume at 20°C). Polymerization began after approximately 10 minutes. The discharge stroke was activated at regular time intervals before polymerization began. The pressure drop measured as a result of this, in this case a drop of 20 bar, is
the desired predetermined loading degree, in this case
This corresponded to the desired value of 87.8%. The controller was now set for a pressure drop of ΔP=20 (desired value) to occur on each discharge stroke. If the pressure drop increases (ie the autoclave is loaded more), the ejection device will eject more quickly, and if the pressure drop decreases, the ejection stroke will become slower. After a few hours, a steady state was established in the autoclave, which was discernible by the regular introduction of ethylene and by substantially uniformly spaced discharge strokes. The following observations were made: (1) The amount of latex released per unit of time from the measuring and controlling device was automatically adjusted within a narrow range as a constant value. Approximately 5.2Kg of latex was generated per hour. This latex is 42±1.0
% solids content and a density of 0.96 g/cm ³ at 22°C. The ejection chamber (empty volume 0.110) was ejected approximately 50 times (50+4 strokes) per hour under the command of the device controlling the degree of loading. (2) The mode of operation controlled by the degree of loading allowed for very regular temperature guidelines. The difference between the temperature within the reactor and the temperature of the cooling jacket was adjusted to be substantially constant. (3) Ethylene is not supplied in a controlled quantity manner, but in a controlled manner, but
The amount of ethylene flowing into the reactor per unit of time was approximately constant. This was an unavoidable consequence of the steady state in the reactor obtained by the controlled discharge operation at the level of loading. (4) The polymerization process could be intentionally made to occur faster or slower. Desired value of degree of loading is low △
When P varies, for example, △P = 10 bar,
A high solids content of the latex was prepared and the heat of polymerization was increased. (5) The slight turbulence that occurs during pumping in aqueous solutions could be easily compensated for by controlling the degree of loading. The polymerization process was completed after 200 hours of operation. 32.7Kg
of latex was present in the autoclave.
Originally, 36.0 kg of polyethylene latex was used.
The degree of loading therefore remained essentially constant during the polymerization process. The walls of the autoclave are approximately 1 mm thick at the top.
The walls where there is a constant presence of a dense liquid phase were not coated. This latex contained only a small amount of agglomerate (approximately 1.5°/00 based on solids). It was very stable to shear forces and could be redispersed in water immediately after drying at room temperature. However, the film heat-treated at elevated temperatures was transparent and waterproof. By adding ethanol, polyethylene could be precipitated from the dispersion as a fine white powder. After suctioning and drying, the viscosity number [η] was determined in tetralin. This polymer dissolved in tetralin in a gel-free state at 120°C. Viscosity [η] = 0.5 (dl/g, in tetralin, 120°C). This latex could be used as a mixed component with other dispersions to improve block strength, could be used in hydrophobized pigments, and was particularly suitable for the production of master batches. Example 5 Continuous production of vinyl chloride-ethylene latex The following solutions were prepared: Aqueous emulsion solution (A) Deionized water 94.15 parts by weight Hydroxyethyl cellulose 0.13 parts by weight Sodium lauryl sulfate 2.00 parts by weight NaHCO ₃ 1.42 parts by weight Acrylamide 2.30 Parts by weight 100.00 parts by weight Activator solution (B) Deionized water 91.89 parts by weight Ammonium peroxodisulfate 7.65 parts by weight Ammonia water, 25% 0.46 parts by weight 100.00 parts by weight Activator solution (C) Deionized water 98.52 parts by weight Sodium formaldehyde sulfoxylate
1.48 parts by weight 100.00 parts by weight A 42.7 autoclave was filled with 38.0 kg of vinyl chloride-ethylene latex (approximately 50%), air was purged from the autoclave chamber with ethylene, and the autoclave was sealed. After heating to 65° C., ethylene was introduced under a pressure of 100 bar. The following streams were then weighed in: Solution A 1750 cm ³ /h Solution B 300 cm ³ /h Solution C 300 cm ³ /h Vinyl chloride 2000 cm ³ /h After starting the polymerization, a controller was installed to control the extent of loading. △ per discharge stroke (discharge ^-1.80cm3 )
A pressure drop of P=1.3 bar was set. This desired value was determined as specifically described in Example 4. Over 200 hours, 920 Kg of latex was produced, corresponding to 4.6 Kg/h. During the polymerization, samples were taken every 20 hours. The following was then determined: 1 Solids content. 2 Average film forming temperature (measured according to DIN 53787). 3 PH value. 4 Drop number latex
(DN) [In an identical droplet counting device (stalagmomoeter), water at 20°C is
When indicating the number of droplets that decompose 1 cm ³ of latex at 20℃]. 5 Centrifugation test: 10 cm ³ of latex was centrifuged at 8000 rpm for 15 minutes in a laboratory centrifuge. The latex was then decanted, and the precipitate that had settled at the tip of the centrifuge tube was redispersed in water, dried, and weighed. The amount of dry sediment per 10 cm ³ of dispersion was recorded. 6 Chlorine content (% chlorine on solids) of the transparent film made by drying the dispersion and subsequent vacuum drying to constant weight. The determined values are shown in Table 4 below. Table 4 Solid content (%) 49.5±2% MFT (℃) 14±2℃ PH value 7.8±0.2 DN, latex 55±0.4 (DN H ₂ O 24±0) Sediment (g/10cm ³ ) 0.32± 0.04 Chlorine content (%) of the transparent film 42.7±0.5 The values shown in Table 4, which vary only slightly, indicate a very uniform reaction. When the same mixture was polymerized without controlling the degree of loading according to the invention, highly variable values were obtained depending on the accuracy of the ethylene feed. The solids content of the latex was then about ±5%, the average film forming temperature was ±6°C, and the chlorine value of the polymer varied about ±2%. When the polymerization was completed, 37.6 Kg of latex was present in the autoclave. 38.0Kg was used.
The degree of loading was therefore kept substantially constant by controlling the degree of loading according to the invention. If this level of loading control is not used, variations in the level of loading can occur, and in extreme cases can even cause the reactor to empty. Latexes produced according to the present formulation can be used as pigment binders for internal and external coatings, as binders for cement mortars and for bonding glass fibers. Example 6 Preparation of a flexible vinyl chloride-ethylene copolymer Example 5 was repeated with the following modifications: 1 The polymerization temperature was increased to 75°C. 2 Instead of the 180 cm ³ discharge chamber, a 110 cm ³ discharge chamber was used. 3 The pressure was increased from 100 bar to 200 bar. and 4 A pressure difference of 6 bar was predetermined for the ejection stroke. Approximately 4.7 kg of latex was produced per hour. The latex had an MFT of 0-5°C. The dried film contained 36.0±1.5% chlorine. Solids content was 46±1.5%. This latex dried into a soft, laminable, but non-adhesive film. The polymer was only partially soluble in tetrahydrofuran. This dissolved part has a viscosity number [η] = 0.8 to 1.0 (25℃, THF)
showed that. Latexes of this type could be used as binders for coating the underside of carpets, in the manufacture of wallpaper and as binders for paper. After approximately 200 hours of operation, the level of reactor loading remained essentially constant. After expansion, approximately 30Kg of latex was present in the autoclave. Approximately 33 kg was introduced first. Example 7 Preparation of a dispersion of vinyl chloride-vinyl acetate-ethylene copolymer The following solutions were prepared (all amounts are parts by weight): Aqueous emulsifier solution A: Deionized water 93.65 Maleic acid semiester sodium salt (1 ) 3.34 Methacrylamide isobutanesulfonic acid sodium salt (2) 0.67 Sodium lauryl sulfate 1.34 Hydroxyethylcellulose 1.00 100.00 Activator solution (B) Deionized water 86.20 Ammonium peroxodisulfate 6.90 Ammonium bicarbonate 6.90 100.00 Activator Solution (C) Deionized Water 98.43 Sodium Formaldehyde Sulfoxylate
1.57 A 100.00 42.7 autoclave was filled with a seed latex at approximately 50% of the desired copolymer composition. After adding 36 Kg of seed latex, the air was purged from the autoclave chamber with ethylene, the autoclave was sealed and heated to 60° C., ethylene was introduced under a pressure of 60 bar and the following streams were weighed in: Solution A 1750 cm ³ /h Solution B 375 cm ³ /h Solution C 375 cm ³ /h Vinyl chloride 1700 cm ³ /h (equivalent to 1630 g/h) Vinyl acetate 710 cm ³ /h (equivalent to 633 g/h) Pressure drop of 1.24 bar to control the degree of loading Adjusted to. The discharge chamber thereby had a volume of 180 cm ³ . 30 samples were removed during 300 hours. The following results were obtained: Latex release/hour: approx. 5.2Kg Solids content: 51.6±0.5% MET: 12.0±1℃ PH value: 5.6±0.2 DN, latex: 39±1 Sediment (g/ ^10cm3 ): 0.75±0.15 Chlorine content (transparent film): 30.6±0.3% Vinyl acetate content (transparent film): 19.2±3% When the polymerization was completed, approximately 36 Kg of latex was present in the autoclave. That is, the degree of loading remained constant. This latex could be stored for two years without forming a precipitate, despite high sediment values upon centrifugation (8000 rpm for 15 minutes). This was most suitable as a binder for internal and external coatings. Example 8 (comparative example) Table 5 shows three samples that can be prepared up to 350 bar.
Four formulations are featured for the discontinuous polymerization of vinyl chloride and ethylene in an autoclave. In these formulations, the same chemicals were used in the aqueous phase as in the experiments of Examples 5 and 6. Apart from monomers, the quantitative amounts of materials used were the same as in Examples 5 and 6. Experiments A to D of this example were carried out as follows: Solution 1 was first introduced into the autoclave of 3, the air was purged from the autoclave chamber with ethylene, then the relevant amount of vinyl chloride was weighed in,
Heated to 65°C. Then the ethylene pressure is initially
80 bar for experiments A and B and for experiments C and D.
The case was adjusted to 200 bar. The activator solution was then rapidly pumped in in about 3 minutes. Immediately after adding solutions 2 and 3, a pressure of 200 bar was set for experiments A and B and for experiment C.
In case of and D a pressure of 250 bar was set by addition of ethylene. Now the pressure inside the container is 100 or
When falling below 250 bar, a pressure-controlled valve opens and subsequently supplies the consumed ethylene. Experiments A and D occur violently and control of temperature is possible only with careful temperature regulation. After the polymerization process lasted for 6 hours, the mixture was cooled to 30 °C and
The contents in the autoclave were expanded. Experiment A
The latexes of and D contained large amounts of agglomerates and for this reason the solids content of the latexes was not determined. The latexes of Experiments B and C contained 10 and 28 g of aggregate. The chlorine content of the copolymers prepared according to formulations A-D is shown in the penultimate line of Table 5. In the case of experiments A and B, carried out at an ethylene pressure of 100 bar, much less ethylene was introduced into the copolymer than in the experiment of Example 6;
The copolymer of Example 6 had a chlorine content of 42.7%;
and Experiments A and B produced products with chlorine contents of 49.2% and 48.1%. However, dispersions based on vinyl chloride-ethylene copolymers with such a composition do not form films at 20 °C;
Therefore, it could not be used as a binder for coatings. In Comparative Example C, a latex was produced that still just formed a film. However, its production required a pressure of 250 bar. Furthermore,
The solids content of these dispersions is only 30% by weight;
ie significantly lower than the approximately 50% by weight value required for commercially common products. Now, when attempting to increase the solids content with additional vinyl chloride, apart from the fact that the polymerization is not easily controlled and agglomerates form, the undesirably high vinyl chloride content in the copolymer A product with . However, in the method of Example 5, 150
Even at pressures as low as 1 bar, not only do copolymers with the required amount of vinyl chloride units polymerized, but also approximately 50% dispersions can be produced in a continuous process. This process is therefore a completely economical process that allows simple circulation of the monomers through a controlled polymerization process.

[Table] Example 9 Continuous copolymerization of ethylene-vinyl acetate 42.7 mm connected to a discharge device (capacity: 0.110)
32 kg of vinyl acetate-ethylene latex was placed in an autoclave. Essentially about 50% stable with no residual monomers
A seed latex, such as the latex prepared according to Example 7, was used as starting material. To this dispersion, 50 g of ammonium peroxydisulfate dissolved in 3 parts of deionized water was added while stirring the solution. The autoclave was sealed and air was purged from the autoclave chamber with ethylene. Room temperature (approx. 22℃)
At , ethylene was introduced under a pressure of 50 bar and the mixture was heated to 65°C. After the required polymerization temperature of 65° C. was achieved, the pressure was set at exactly 200 bar. The stirring speed was 120 rpm. The following solutions were now weighed out: Solution 1 Water 97.12 parts by weight (NH ₄ ) ₂ S ₂ O ₈ 0.85 parts by weight C ₁₂ -C ₁₈ alkylsulfonic acid Na salt 0.90 parts by weight Hydroxyethylcellulose 0.70 parts by weight NaHCO ₃ 0.45 parts by weight 100.00 parts by weight Solution 2 Water 96.04 parts by weight Sodium formaldehyde sulfoxylate,
NaSO ₂ CH ₂ OH 2.00 parts by weight Na-alkylsulfonate mixture, as solution 1 1.96 parts by weight 100.00 parts by weight Pumped per unit of time: Solution 1 2900 cm ³ /hour (20°C) Solution 2 300 cm ³ / Vinyl acetate 1200 cm ³ /hour (20° C.) By using the discharge device, approximately 55 strokes per hour were first carried out until polymerization started after 1 to 1 1/2 hours. The automatic restriction of the degree of loading was then set to the desired pressure drop of 15 bar. The mixture is reacted in a completely controlled manner, thereby consuming a considerable amount of ethylene. Approximately 5.7 kg of latex was released every hour. This latex had a viscous consistency. A latex with a solids content of about 46% and a PH value of 5 dried into a non-adhesive film. This polymer was dissolved in hot toluene, for example. This is viscosity number [η] (dl/g) at 90℃ in toluene =
It had 1.28. Only trace amounts of the gel portion were present. After 100 hours of operation, 32.7 Kg of dispersion was present in the autoclave. That is, the degree of loading remained virtually constant. Vinyl acetate in the film is approximately
It remained constant at 35±2%. This polymer formed a soft sheet that was easily rolled up and had a Mooney viscosity of 13. After crosslinking with peroxide, it can be used as a grafting base for impact-resistant plastic materials. Grafting can be carried out in solution and in emulsion. Polymerization reactions were also carried out at the same ethylene pressure by using a monomer mixture consisting of 99 parts by weight of vinyl acetate and 1 part by weight of a crosslinking agent such as divinyl adipate or norbornadiene. Latexes of this type were particularly well suited for the production of impact-resistant PVC. Example 10 (Comparative Example to Example 3) Vinyl Acetate-Ethylene Quasi-Continuous Polymerization Process A solution of the following components was introduced into a 42.7 autoclave: 15000 g deionized water 60 g ammonium peroxydisulfate Sodium alkanesulfonate as in Example 9 salt
50g Hydroxyethylcellulose as in Example 9 100g NaHCO ₃ 40g Air was then forced out of the autoclave chamber;
Ethylene was replaced and 1350 g of vinyl acetate were introduced at room temperature with stirring (120 rpm). Ethylene was then added at room temperature under a pressure of 100 bar and the mixture was heated to 60°C. When it reaches this temperature,
Ethylene was introduced under a pressure of 180 bar. Also water (deionized) 375.0g Sodium formaldehyde sulfoxylate
18.35 g of solution was pumped in over a period of 10 minutes. The temperature was maintained at 65°C for 1 hour, then the ethylene pressure was increased.
The pressure was increased to 200 bar. The following streams were then weighed out over a 7 hour period: Solution 1: Deionized water 1000.0g Hydroxyethyl cellulose 13.3g Sodium formaldehyde sulfoxylate
18.35g Sodium alkanesulfonic acid salt as in Example 9
20.00g Solution 2: Deionized water 3000.00g Ammonium peroxydisulfate 93.80g Hydroxyethylcellulose 13.3g Sodium alkanesulfonic acid salt as in Example 9
129.7g NaHCO ₃ 37.82g and vinyl acetate 8100g. Polymerization started after activation and became more intense as time progressed. When all ingredients are added,
The mixture was stirred for 3 hours while maintaining a pressure of 200 bar and then expanded at 60°C. According to the mixture, 34-37 kg of dispersion with a solids content of approximately 44-46% by weight were obtained from this. This dispersion dried into several adhesive films. The polymer contained 48-53% vinyl acetate. The polymers also had highly variable gel contents, amounting to as much as 35%. The soluble part has a viscosity number [η] =
0.6-1.0 (dl/g) (90°C, toluene). Thus, the polymer of the comparative formulation was fundamentally different from the product according to Example 9 in which substantially more ethylene was introduced. Example 11 Preparation of a self-crosslinkable vinyl chloride-ethylene copolymer Example 6 was repeated except that instead of using aqueous solution (A) (Reference Example 5), the following solution was used: Deionized water 90.15 Parts by weight Redroxyethyl cellulose 0.13 parts by weight Sodium lauryl sulfate 2.00 parts by weight NaHCO ₃ 1.42 parts by weight Acrylamide 2.30 parts by weight N-methoxymethylacrylamide 4.00 parts by weight 100.00 parts by weight This solution was pumped in at 1750 cm ³ /h. Other streams B, C and vinyl chloride (Reference Example 5) were retained. Approximately 4.6 kg of latex was produced per hour. This latex had an MFT of 5-8°C.
Dry latex film contains 37% chlorine by weight
Contained. The solids content of the latex was approximately 45% by weight. Degassed latex adjusted to pH 7 using soda ash and optionally added with conventional PVC stabilizers.
It could be used as a binder in textile printing. It was characterized by outstanding redispersibility and color yield, and the pigment retention of benzene-rich and benzene-free pigment paste systems was excellent. This binder can be compared in its robustness with the best conventional binders on the market, but it is produced with a substantially cheaper monomer system and at the same time with a simple manufacturing process. The binder of the present invention differs from binders of similar composition that can be produced according to a quasi-continuous process due to the improved resolubility, which is based on the wide latex particle diameter distribution of the binder according to the present invention. . Of course, instead of N-methoxymethylacrylamide, other known crosslinking agents could also be used, such as N-methylolmaleic acid amide.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a specific example of the measurement and control method according to the present invention, and FIG. 2 is a flow diagram showing equipment for applying the method of the present invention.
FIG. 3 represents the pressure drop that occurs per ejection stroke, and FIG. 4 compares experimental and calculated pressure drop versus degree of loading.

Claims (1)

[Scope of Claims] 1 Polymerization by continuous polymerization of gaseous or gaseous and liquid monomers in the presence of a liquid phase in a pressurized reactor in which the degree of loading is maintained constant. A method for producing a combined dispersion in which the degree of loading is determined continuously by regular and repeated changes in pressure brought into a reactor of constant initial pressure and constant temperature, and the monomer and liquid Polymer dispersion characterized in that the addition of phases and/or the removal of reaction products is increased or decreased, respectively, by using automatic measurement and control systems, so that the degree of loading of the reactor is kept constant. Liquid manufacturing method. 2. Removal of the reaction product from the product discharge chamber in strokes, the extent of loading being known by the resulting pressure change in the reactor, and the subsequent discharge stroke being adjusted accordingly to the extent of loading of the reactor. 2. A method according to claim 1, wherein the time is adjusted so that the degree remains constant. 3. Claim 1 wherein the polymer dispersion is produced by carrying out the polymerization in the presence of an aqueous phase.
The method described in section. 4. The manufacturing method according to claims 1 to 3, wherein dispersions of ethylene homopolymers and copolymers are manufactured by polymerizing ethylene and optionally other monomers. 5. The method according to claim 4, wherein an aqueous dispersion of a copolymer is produced by copolymerizing ethylene and vinyl chloride and/or vinyl acetate.